1. Field of the Invention
The present invention generally relates to a fixing device and an image forming apparatus provided with the fixing device and more particularly to a fixing device for improving fixation of a visualized image on a recording medium in a simple structure and an image forming apparatus provided with the fixing device.
2. Description of the Related Art
Conventionally, in the field of image forming apparatuses using electrophotography such as copier, printers, facsimile devices, and the like, there have been methods for improving the fixation of a visualized image of toner carried on a recording medium. General examples of such methods involve heat fixing methods in which toner images are fixed by heating a rotatable head fixing roller from the inside using a heater, the fixing roller elastically deforming a surface of the recording medium, and by pressing an endless belt capable of conveying while being in contact with the heat fixing roller from an opposite side relative to contact face using a pressure roller.
Regarding the above-mentioned heat fixing methods, there are nip fixing methods for pressing using a pressure pad made of rubber instead of the pressure roller pressing from the opposite side and conveying the recording medium using a belt rotating on a surface of the pressure pad so as to achieve a small size and improve efficiency (refer to Patent Document 1, for example). Further, it is known that when a pressure range of the pressure pad is increased, low-energy fixing is realized.
Patent Document 1: Japanese Laid-Open Patent Application No. 8-262903
However, when the pressure range of the pressure pad is increased, because of a load for pressing the pressure pad, plural pressure units such as springs are required as disclosed in Patent Document 1, so that the cost is increased. Further, in the fixing method as disclosed in Patent Document 1, when the springs are incorporated in a pressure applying unit including the pressure pad, a diameter of the endless belt is increased and an entire portion of the apparatus is enlarged.